Heater fault duet shield Mendel 3

Recently I installed the duet shield on my Mendel 3 and now the heater faults in heater 1 and 2 while heating up near the end temperature. Thermistor 3 appears to be fine. Oddly if I bring them to 170 and then increase to 195 they don't fault. I've had them up to 235C without fault, but if I warm them from room temp to 195 or a higher temp thermistor 1 an 2 fault. I've gone through the wires, connections, and board but haven't found the problem.

Any ideas?

I think I know the problem now, after using prontoface I see the response from the unit, it appears the heater is taking too long. I suspect the reason is two fans instead of on and it is taking too long to heat up. I need to slow down the fans now there are two of them.

I disconnected the other fan and it still faults from too much time expired. Perhaps the duet shield is causing the slowdown? It will almost make temp but not fast enough.

It appears the additional mass of the second hot end is too much for the firmware to keep it at temperature. For example, if the temperature is set for 205 it will increase in temperature quickly to 185 and then snail crawl to 200 and never reach 205. This only happens on heater 1 and 2 which are combined on the same heat sink whereas the third hot end has no problem reaching and maintaining temperature.

User error.... When I set the two new extruders I placed them against the heat sink block which caused the heating problems; there's supposed to be a 3mm gap between the two.

Lesson learned. Hopefully, if someone else has this issue they can learn from my mistake.

Krosser what mendel do you have ?

Mendel 3 Tricolour. Setting the tips all to the same height is challenging!